Antenna system



. P 0- w. M. HAHN EMANN 2,213,859

I. ANTENNA SYSTEM Filed June 22, 1938 l/femq fe/ Opera f/ we L Ca go/1779 means I [cup/ivy men 115 I I I I I I I I I Transmiffer film/710m-Mlle/- Max (labile/11mm y MW? flllgrne Patented Sept. 3, 1940 ANTENNASYSTEM Walter Max Hahnemann, Berlin, Germany, assignor to C. LorenzAktiengesellschaft, Berlin- Tempelhof, Lorenzweg, Germany, a companyApplication June 22, 1938, Serial No. 215,138

In Germany May 15, 1937 7 Claims.

The present invention relates to antenna systems and has for its objectto eliminate the interfering silent zones of the radiation diagramsproduced by such systems.

The radiation diagram obtained in connection with antenna systemsprovided on towers at a certain distance above the earths surfacerepresents a number of leaves which are set up on account of theinterference between the direct radiation from the antenna and by theradiation reflected from the earths surface.

The invention consists in certain features of novelty which aredisclosed in the following description and pointed out in the appendedclaims, reference being made to the accompanying drawing, in which:

Fig. 1 diagrammatically illustrates the radiation pattern of a knownantenna system; Fig. 2 is a diagrammatic representation in details of aradiation pattern obtained according to the invention; Fig. 3 shows theresulting effective radiation pattern according to the invention; whileFig. 4 schematically illustrates the antenna system according to theinvention.

The radiation diagram shown in Fig. 1 shows the leaves above referredto. The number and the form of these leaves and the intermediate silentzones depend upon the operating wavelength and the height of the antennasystem above the earths surface. The ratio between these magnitudes isparticularly high within the range of ultra short waves so that a verygreat number of leaves are obtained. Such radiation diagrams aredisadvantageous in many respects, for instance, in connection withwireless communication with aircrafts since the great number of silentzones is troublesome on approaching the transmitter. This disadvantageis particularly accentuated in cases that such transmitters are intendedfor use in wireless navigation.

The invention has for its object to eliminate the troublesome silentzones of a radiation diagram. The invention proposes the application ofa second radiating structure the radiation pattern of which is so formedthat its maxima are located where the minima of the actual antennaradiation pattern are located.

It has already been mentioned that the number and the shape of theleaves and of the silent zones may be adjusted by correspondinglydimensioning the height of an antenna system above the earths surface.two radiating structures is so dimensioned according to a furtherfeature of the invention The height of the that the desired overlappingbetween the two radiation patterns is secured. The second additionalradiation structure is thus placed either above or below the actualradiating system.

Fig. 2 illustrates two radiation patterns in which the individual leavesare so dimensioned with respect to their number and their shape that theminima of one radiation pattern coincide with the maximum of each leafof the second radiation'pattern. One of these patterns is indicated inthe Fig. 2 by means of thick lines while the second pattern is hatched.It is thus obvious that the original maxima and minima of the radiationpattern have been equalized so that a useful diagram is obtained asshown in Fig. 3.

The coupling between the twoantenna structures arranged one above theother may be accomplished in difierent manners. Both antenna structuresmay be fed over energy lines from a transmitter common to both antennastructures. It is also possible to feed one antenna structure only fromthe transmitter, while coupling the second antenna structure by means ofradiation. On the other hand, a galvanic, an inductive or a capacitivecoupling may be employed. g

One embodiment of the novel antenna a rrangement is illustrated in Fig.4. A tower I carries one antenna system 2 and a second antenna system 3arranged below the first mentioned system. The heights above the earthssurface at which the two systems are arranged are so dimensioned thatthe minima of one radiation pattern coincide with the maxima of thesecond system. The main system 2 is fed by the transmitter S over anenergy line 4. The additional system 3 is coupled to the system 2 eitherby means of radiation or galvanically, inductively or capacitivelythrough the coupling device 5.

In cases that the antenna arrangement above described shall be employedfor aircraft navigation, alternately keyed reflectors may be allotted tothe antenna structures 2 and 3, whereby the reflectors may be coupledwith one another in any known manner.

The compensation of the silent zones is not necessarily to beaccomplished by virtue of a second antenna arrangement. For instance, itis possible to provide means such as metal sheets, wire meshes and thelike so as to produce the desired interference with respect to thesilent zones.

What is claimed is:

1 tion pattern from said second antenna.

2. An antenna arrangement comprising two antenna systems for producingradiation patterns each having a plurality of maximum and minimum pointsin vertical planes, said antenna systems being arranged one above theother and spaced above the earth distances such that the minima of theradiation pattern produced by one antenna system coincide with themaxima of the radiation pattern produced by the second antenna system.

3. An antenna arrangement comprising two antenna systems for producingradiation pat terns each having a plurality of maximum and minimumpoints in vertical planes, said antenna systems being arranged one abovethe other and above thesurface of the earth so that the minima of theradiation pattern produced by one antenna system coincide with the ofthe radiation pattern produced by the second antenna system, and. anoscillation generator cornrnon to both antenna systems for feeding thesesystems.

4. An antenna arrangement comprising two antenna systems for producingradiation patterns each having a plurality of maximum and minimum pointsin vertical planes, said antenna systems being arranged one above theother and spaced above the earth such distances that the minima of theradiation pattern produced by one antenna system coincide with themaxima of the radiation pattern produced by the second antenna system,an oscillation generator for feeding one of said antenna systems, andmeans for coupling the other antenna system to the fed antenna system.

5. An antenna system for producing a radiation pattern relatively freefrom field strength variations in the vertical plane, comprising anantenna spaced above the earth for producing a radiation patterninherently having a plurality of maximum and minimum zones in a verticalplane, and additional conductive means arranged below said antenna forequalizing radiation in the minimum zones intermediate said radiationpattern maximum zones.

6. An antenna arrangement for the purpose of navigating aircraft,comprising two antenna systems for producing radiation patterns eachhaving a plurality of maximum and minimum points in vertical planes,said antenna systems being arranged one above the other and spaced abovethe earth such distances that the minima of the radiation patternproduced by one antenna system coincide with the maxima of the radiationpattern produced by the second antenna system, an oscillation generatorcommon to both antenna systems for feeding these systems, alternatelykeyed reflectors arranged on either side of both antenna systems, andmeans for coupling said reflectors to one another.

7. An arrangement for the purpose of navigating aircraft, comprising twoantenna systems for producing radiation patterns each having a pluralityof maximum and minimum points in vertical planes, said antenna systemsbeing arranged one above the other and spaced above the surface of theearth a distance such that the minima of the radiation pattern producedby one antenna system coincide with the maxima of the radiation patternproduced by the second antenna system, an oscillation generator adaptedto feed one of said antenna systems, means for coupling the otherantenna system to the fed antenna system, alternately keyed reflectorsarranged on either side of both antenna systems, and means for couplingsaid reflectors to one another.

WALTER MAX HAHNEMANN.

